Robertson went on the DL last week with a lower back strain after he injured himself working out in Cleveland. His back locked up on him during an off-day in Minnesota, leaving him unavailable for the series against the Twins, but a combination of anti-inflammatories and therapy loosened up his back a few days ago. He was able to complete a throwing session and was cleared for action.
Robertson has allowed seven runs on 10 hits in 10 innings this season, walking six and striking out seven. He serves as both a second lefty reliever behind setup man Bobby Seay and a long relief option alongside Zach Miner.
Detroit made room for Robertson's return after Wednesday's game by optioning left-hander Luke French to Triple-A Toledo.
The Tigers could make another move after Thursday's game to bring back Magglio Ordonez from the family medical emergency list.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.